Bolt retainer and compressor employing same

ABSTRACT

The disclosure shows a sealing member secured to the inner end of a compressor stator vane row by bolts and nuts. One form of bolt retainer prevents a loosened bolt from entering the flow field. The retainer is of hollow, box-like cross section with keyhole slots in its inner wall for assembly and access holes in its outer wall for insertion of an allen wrench to torque the bolts. Another form of bolt retainer provides access to the outer portion of the bolt heads so that they may be tightened and loosened. A third form of retainer may be assembled laterally and comprises a plate and retainer lugs for the bolts.

United States Patent 1191 Burge 1 Apr. 17, 1973 1 BOLT RETAINER ANDCOMPRESSOR 3,186,465 6/l965 Hayunga ..|51/41.71

EMPLOYING SAME i Primary Examiner-Edward C. Allen [75] Inventor Josephnurgecmcmnan Ohm Attorney-Derek P. Lawrence, Frank L. Neuhauser, [73]Assignee: General Electric Company, Lynn, Oscar B. Waddell, Joseph B.Forman and Edward S.

Mass. Roman [22] Filed. Feb. 16, 1971 ABSTRACT [21] Appl' 115273 Thedisclosure shows a sealing member secured to the inner end of acompressor stator vane row by bolts [52] US. Cl. ..15l/69, 151/4171,415/172 and nuts. One form of bolt retainer prevents a 511 1111.01..Fl6b 41/00 loosened bolt from entering the flow field- The [58] Fieldof Search ..15 1/69, 41.71; retainer is of hollow, box-like Crosssection with 287/139 36 F keyhole slots in its inner wall for assemblyand access holes in its outer wall for insertion of an allen wrench 56]References Cited to torque the bolts. Another form of bolt retainerprovides access to the outer portion of the bolt heads so UNITED STATESPATENTS that they may be tightened and loosened. A third form ofretainer may be assembled laterally and comprises a 2,800,247 7/1957Appleton ..l5 l/69 plate and retainer lugs for the bolts 2,645,3177/1953 Staaf ..287/189.36 F 3,170,473 2/1965 Downs et al ..l5 H69 6Clains, 6 Drawing Figures 2,907,4l9 10/1959 Klank ..l5l/69 PATEMED3.727. 660

SHEET 2 BF 2 INVENTOR. JOSEPH c. SURGE mummy- BOLT RETAINER ANDCOMPRESSOR EMPLOYING SAME The invention described and claimed in theUnited States patent application herein resulted from work done underUnited States Government contract F A-SS-67-7. The United StatesGovernment has an irrevocable, non-exclusive license under saidapplication to practice and have practiced the invention claimed herein,including the unlimited right to sublicense others to practice and havepracticed the claimed invention for any purpose whatsoever.

The present invention relates to improvements in fasteners having boltretainers and, in more limited aspects, to a compressor employing same.

Axial flow compressors comprise a rotor having one or morecircumferential rows of cambered airfoil blades. Downstream of eachblade row there is a circumferential row of stator vanes mounted on theouter casing of the compressor. It is desirable to removably mountcircumferential sealing members on the inner ends of the vanes. Suchsealing members cooperate with teeth on the rotor to minimize pressurelosses.

When bolts are employed to secure these sealing members, self-lockingnuts, such as those having a plastic insert, are used to preventloosening of the bolts. Even so, the extreme vibrations encountered inopera tion cause the bolts to loosen and, in rare cases, to disengageand enter the flow field of the compressor. Such an occurrence can causeextensive damage to the compressor blading as well as to the blading ofturbines commonly in series flow relationship with compressors. Eventhough this happens rarely, the extensive damage which can result makesit necessary to provide more positive retention of these bolts.

The use of rivets or tack welding of the bolt heads would provide apositive retention of the fasteners. This solution is undesirable sinceit makes removal of the sealing member for maintenance purposesdifficult and time consuming. I

Accordingly, one object of the invention is to provide an improvedfastening means for the sealing mem bers of axial flow compressorsta'tor vanes which greatly minimizes, if not'eliminates, thepossibility of an attaching bolt entering the compressor flow fieldwhile at the same time provides for easy assembly and disassembly.

Another and broader object of the invention is to provide an improvedbolt retainer which can be used in combination with standard bolts.

These ends are attained by a fastener which includes a plurality ofspaced bolts threaded into internally threaded members. A bolt retainerof hollow, box-like cross section has keyhole slots spaced in the samefashion as the bolts. The large ends of the keyhole slots telescope overthe bolt heads permitting the retainer to be indexed to bring the boltbodies into the small ends of the keyhole slots. Openings in the outerwall of the retainer are aligned with the small ends of the keyholeslots. These outer openings are smaller than the heads of the bolts andlarge enough for insertion of a torquing tool to engage torquingsurfaces on the bolt heads. The bolts may thus be tightened to clamp theinner wall of the retainer.

Where the bolts have collars at the bases of their heads, the exteriorheight of the hollow, box-like retainer is less than the height of thebolt head and its interior height is somewhat greater than the height offaces on the periphery of the bolt head as well as the retentionfunction. v

The box-like cross section of the retainer provides rigidity againstinduced vibrations with a minimum of weight. Where this feature is notrequired, the retainer may take the form of an elongated plate havingholes which receive the bodies of the bolts and lugs that overlieportions of the bolt heads.

In attaching sealing members to stator vanes, the bolts are disposed inangularly spaced relation and the bolt retainers are arcuate segments.

The above and other related objects and features of the invention willbe apparent from a reading of the following description of thedisclosure found in the accompanying drawings and the novelty thereofpointed out in the appended claims.

FIG. 1 is a fragmentary view, in longitudinal section, of an axial flowcompressor;

FIG. 2 is an enlarged view of a novel fastener employed in thecompressor of FIG. 1;

FIG. 3 is a section taken on line III-III in FIG. 2;

FIG. 4 is a view, similar to FIG. 2, illustrating another embodiment ofthe invention;

FIG. Sis a section taken on line VV in FIG. 4; and

FIG. 6 is a fragmentary, perspective view of a further embodiment of theinvention.

FIG. 1 illustrates the forward portions of an axial flow compressorwhich comprises an appropriately journaled rotor 10. The rotor maycomprise a series of discs 12 having cambered airfoil blades 14 mountedaround their peripheries. Downstream of each blade row is a row ofcambered airfoil stator vanes 16 mounted on the compressor casing (notshown). The inner ends of the stator vanes (in a given row) are mountedon a shroud 18. A circumferential sealing member 20 is connected to theshroud 18 by fastening means 22. In many cases the compressor casing isformed by two semicylindrical shells joined together at longitudinalsplit lines. In such a case, the sealing member could be formed by twosegments. The sealing member has abradable surfaces 24 which cooperatewith sealing teeth 26 on the rotor 24 to minimize flow losses across thestator stage. In order that the sealing surfaces may be repaired orreplaced,

the sealing members are removably secured to the' shrouds 18 by thefastening means 22 which will now be described in detail with referenceto FIGS. 2 and 3.

Nuts 24 are captured on the inner surface of the sealing memberstructure by a retainer 26 secured thereto. Bolts 28 pass throughaligned holes in overlapping radial flanges 29 and 30 to the shroud l8and sealing member, respectively. The bolts 28 also pass through keyholeslots 31 in the inner wall of a bolt retainer 32. The bolt retainer hasan arcuate length sufficient for at least two or more keyhole slotS 31so that it will be clamped by two or more bolts. The bolt retainer is ofhollow, box-like configuration sufficient to accommodate the heads ofthe bolts 28.

In assembly the bolts 28 are partially threaded into the nuts 24. Thebolt retainers are then telescoped over the heads of the bolts whichreadily pass through the larger portions of the keyhole slots 31. Eachbolt retainer is then indexed to register the smaller portions of thekeyhole slots with the body portions of the bolts as illustrated. Holes34 in the outer wall of the bolt retainer are aligned with the smallerportions of the keyhole s1ots.31. When the bolt retainers are thusindexed access is provided for insertion of a wrench (not shown) througha hole 34 and into a noncircular socket 36 formed centrally in the outersurface of each bolt head. Each bolt may thus be turned to firmly clampthe flanges 29 and 30, and the inner wall of the bolt retainer 32together.

The nuts 24 are preferably of the self-locking type, as for example thekind that have plastic plugs deformed by the bolt threads. Nonetheless,the severe vibrational environment of this fastener application mightcause an individual bolt to loosen. Even should this occur, the chancesof any fastener components coming loose and entering the flow path ofthe compressor, where damage could result, are remote in the extreme.Should a single bolt loosen, it could not escape from the retainer sincethe holes 34 are smaller than the heads of the bolts. The remainingbolts 28 secure the retainer 32 in place so that the loose bolt 28 isrestrained from entering the compressor flow field. With thisarrangement, all bolts of a given retainer must loosen before there is apossibility of a bolt coming loose. To even further minimize thepossibility of a fastener element entering the flow field, the boltretainers on each casing half jointly form an angle of about 180 withtheir adjacent ends being closely spaced as illustrated in FIG. 3. Thus,when the casing halves are joined, none of the bolt retainers can indexto bring the large ends of the keyhole slots 31 into register with thebolt heads except in the unlikely event that all bolts would loosen andall bolt retainers would index.

FIGS. 4 and 5 illustrate another embodiment of the inventionparticularly adapted for a type of bolt commonly employed in gas turbineengines. These bolts, indicated at 38, have fluted heads 40 with anintegral, enlarged collar 42 at the bases of the heads. The bolts 38again pass through holes in the flanges 29 and 30 and are threaded intocaptured nuts 24 as before. The bolts pass through keyhole slots 43 inthe inner wall of a retainer 44 with the collars 42 clamped against thisinner wall.

Assembly is essentially the same as previously described. The bolts 38are partially threaded into the nuts 24. The bolt retainer is telescopedover the heads of the bolts, the collars 42 passing through the largeends of the keyhole slots 43. The retainer 44 is also of hollow,box-like cross section but has a height less than the bolt head and aninterior height slightly greater than that of the bolt head collar 42.The fluted end portions 40 of the bolt heads extend through slots 46 inthe outer wall of the retainer permitting the retainer to be indexed tothe locking position illustrated. The flutes or torquing surfaces arethus accessible to a wrench so that they may be tightened duringassembly and loosened during disassembly.

The box-like cross section of the described retainers is highlyimportant in fasteners employed on a compressor rotor. This featuregives rigidity to the retainer which prevents vibrations from beinginduced therein which would cause cracking of the retainer. A crackedretainer could permit a bolt to loosen and both the bolt and the crackedportion of the retainer would then become a hazard should they enter theflow field of the compressor.

This type of vibration, however, does not exist in all instances, inwhich case the embodiment of FIG. 6 could be employed. In FIG. 6 bolts38 (one is shown') again secure the flanges 29 and 30, being threadedinto captured nuts as before. A retainer 48 is provided for a pluralityof bolts 38. This retainer comprises an elongated plate portion 50corresponding to the inner walls of the previously described retainers.Slots 52 are formed in this plate with inner portions thereof receiv ingthe bodies of the bolts. The slots 52 have enlarged openings 54 at theinner side of the plate portion to permit an angular sector for severalbolts to be assembled laterally and then indexed to the illustratedposition. in this position lugs 56, integral with the plate portion 50,overlie the bolt head collar 42 and function in the same fashion as theslotted portions of the outer walls of the previously describedretainers.

While certain aspects of the invention are directed to the describedapplication of attaching sealing members to the inner shrouds of axialflow compressors, other and broader aspects of the invention aredirected to improved fastening means for a wide variety of applica-'tions. The spirit and scope of the present inventive concepts aretherefore to be derived solely from thefollowing claims.

Having thus described the invention, what is claimed as novel anddesired to be secured by Letters Patent of the United States is:

1. A fastener comprising a plurality of internally threaded elements, i

a plurality of headed bolts respectively threaded into said elements,each bolt having torquing surfaces on its head, and a collar at the baseof the bolt head, a box-like crosssection bolt retainer including anelongated plate-like portion having a plurality of elongated slotsspaced apart along the longitudinal length thereof, having large endswhich register respectively with and pass over the heads of said boltsand small ends which respectively receive the bodies of the bolts as thebolt heads clamp the plate-like element, and further including anintegral elongated retainer portion overlying portions of the bolt headand providing access to the torquing surfaces thereof wherein theexternal height of the box-like cross-section is less than the height ofthe bolt heads and the interior height of the box-like cross-sectionapproximates the height of the bolt head collar, and

slots are provided in the outer retainer portion of the bolt retainer inoverlying relation to said elongated slots, the width of said outerslots being sufficiently large for the bolt heads to projecttherethrough but small enough to prevent the collars from passingtherethrough.

2. The fastener of claim 1 for clamping two overlapping arcuate flangeswherein:

the bolt retainer is arcuate along the longitudinal length thereof forabutting engagement against an outside surface of said overlappingarcuate flanges,

6 and the internally threaded members take the form height of thehollow, box-like cross-section is suffiof captured nuts for engagementagainst the opcient to receive the entire bolt head and openings posingoutside Surface Of Said overlapping arcuat are provided in the outerretainer portion of the flanges with the bo ts exten ing t ro gh Saidbolt retainer in registration with the smaller ends flanges. 5

of the keyhole slots said openings being sufficiently large enough forinsertion of a torquing tool into said sockets and small enough toprevent the bolt head from passing therethrough. 5. The fastener ofclaim 4 for clamping two overlapping arcuate flanges wherein:

3. The fastener of claim 2 wherein said bolt retainer is formed as anannulus with inadvertent circumferential indexing occurring only whenall bolts become loosened.

4. A fastener comprising a plurality of internally threaded elements, aplurality of headed bolts respectively threaded into said elements, eachbolt having torquing surfaces on its head provided by a non-circularsocket in the outer end thereof,

a box-like cross-section bolt retainer including an elongated plate-likeportion having a plurality of keyhole slots spaced apart along thelongitudinal length thereof for abutting engagement against an outsidesurface of said overlapping arcuate flanges,

of captured nuts for engagement against the opthe bolt retainer isarcuate along the longitudinal and the internally threaded members takethe form length thereof, having large ends which register posingout.side Surface of Said oYerlappmg l respectively with and pass overthe heads of said g g wlth the bolts extendmg through said bolts andsmall ends which respectively receive the anges v bodies of the bolts asthe bolt heads clamp the 6. The fastener of claim 5 wherein said boltretainer platemke elemm and further including an is formed as an annuluswith inadvertent circum-' tegral elongated retainer portion overlyingpop ferential indexing occurring only when all bolts become tions of thebolt head and providing access to the loosened torquing surfaces thereofwherein the interior

1. A fastener comprising a plurality of internally threaded elements, a plurality of headed bolts respectively threaded into said elements, each bolt having torquing surfaces on its head, and a collar at the base of the bolt head, a box-like cross-section bolt retainer including an elongated plate-like portion having a plurality of elongated slots spaced apart along the longitudinal length thereof, having large ends which register respectively with and pass over the heads of said bolts and small ends which respectively receive the bodies of the bolts as the bolt heads clamp the plate-like element, and further including an integral elongated retainer portion overlying portions of the bolt head and providing access to the torquing surfaces thereof wherein the external height of the box-like cross-section is less than the height of the bolt heads and the interior height of the box-like cross-section approximates the height of the bolt head collar, and slots are provided in the outer retainer portion of the bolt retainer in overlying relation to said elongated slots, the width of said outer slots being sufficiently large for the bolt heads to project therethrough but small enough to prevent the collars from passing therethrough.
 2. The fastener of claim 1 for clamping two overlapping arcuate flanges wherein: the bolt retainer is arcuate along the longitudinal length thereof for abutting engagement against an outside surface of said overlapping arcuate flanges, and the internally threaded members take the form of captured nuts for engagement against the opposing outside surface of said overlapping arcuate flanges with the bolts extending through said flanges.
 3. The fastener of claim 2 wherein said bolt retainer is formed as an annulus with inadvertent circumferential indexing occurring only when all bolts become loosened.
 4. A fastener comprising a plurality of internally threaded elements, a plurality of headed bolts respectively threaded into said elements, each bolt having torquing surfaces on its head provided by a non-circular socket in the outer end thereof, a box-like cross-section bolt retainer including an elongated plate-like portion having a plurality of keyhole slots spaced apart along the longitudinal length thereof, having large ends which register respectively with and pass over the heads of said bolts and small ends which respectively receive the bodies of the bolts as the bolt heads clamp the plate-like element, and further including an integral elongated retainer portion overlying portions of the bolt head and providing access to the torquing surfaces thereof wherein the interior height of the hollow, box-like cross-section is sufficient to receive the entire bolt head and openings are provided in the outer retainer portion of the bolt retainer in registration with the smaller ends of the keyhole slots said openings being sufficiently large enough for insertion of a torquing tool into said sockets and small enough to prevent the bolt head from passing therethrough.
 5. The fastener of claim 4 for clamping two overlapping arcuate flanges wherein: the bolt retainer is arcuate along the longitudinal length thereof for abutting engagement against an outside surface of said overlapping arcuate flanges, and the internally threaded members take the form of captured nuts for engagement against the opposing outside surface of said overlapping arcuate flanges with the bolts extending through said flanges.
 6. The fastener of claim 5 wherein said bolt retainer is formed as an annulus with inadvertent circumferential indexing occurring only when all bolts become loosened. 